Pathological conditions resulting from the hyperproliferation of cells, such as cancer, are a leading cause of death in humans. Current treatment protocols for pathological conditions caused by inappropriate cell proliferation include chemotherapy and radiation. Although these treatment protocols have met with some success, there is a continuing need for drugs that can effectively treat diseases caused by uncontrollable cell growth. Proteasome inhibitors are a new class of promising inhibitors which appear to be more effective and active in cancer cells compared with normal cells, thus providing a distinct advantage over other drugs which do not distinguish between cancerous and normal cells. Proteasome inhibitors are also considered useful for the treatment of many other diseases and pathological conditions.